Faculty Publications
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Publications by NITK Faculty
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Item Low voltage, low power transconductor for low frequency Gm-C filters(Springer Verlag service@springer.de, 2017) Hanumantha Rao, G.; Rekha, S.A low voltage, low power bulk-driven transconductor for low frequency Transconductance-C (Gm - C) filters filters is proposed. The transconductor is designed in UMC 180nm technology with supply voltage of 0.5V. The transconductance (Gm) is tunable from 12nS to 100nS, which is suitable for low frequency Gm - C filters. The power consumption is 120 nW. As an application, a 2nd order Butterworth low pass filter (LPF) with cutoff frequency tunable from 110Hz to 960Hz is designed. © Springer Nature Singapore Pte Ltd 2017.Item Low voltage current reference circuit with low temperature coefficient(Institute of Electrical and Electronics Engineers Inc., 2018) Amaljith, M.K.; Hanumantha Rao, G.; Rekha, S.Current references are necessary building blocks of every integrated circuit where they are used for biasing analog circuits such as filters, oscillators, phase locked loops, etc. This paper describes the design of a low voltage, low power 10 nA current reference. The proposed current reference circuit is based on a simple design methodology which uses the principle of subtraction of two positive temperature coefficient currents. The circuit is made to operate in sub-threshold region with a supply voltage of 0.5 V. The proposed circuit has been designed and simulated in Cadence Virtuoso with gpdk 180-nm CMOS process. The temperature coefficient of the reference current is 186 ppm/° C over a range from 0 to 80° C and the variation with supply voltage is 8.02%/V. The total power consumption of the circuit is as low as 45.887 nW. © 2018 IEEE.Item A 0.5 V, 1 nA Switched Capacitor PTAT Current Reference Circuit(Institute of Electrical and Electronics Engineers Inc., 2019) Hanumantha Rao, G.; Rekha, S.This paper presents a low voltage, low power Proportional to Absolute Temperature (PTAT) current reference circuit. Switched capacitor is used instead of a large resistor, which in turn reduces the area of the circuit and makes the circuit less process sensitive. The proposed circuit has been designed using UMC 65 nm CMOS technology and simulated in Cadence Virtuoso. It generates a reference current (Iref) of 1 nA at 0.5 V supply voltage (Vdd) at room temperature (27°C) and follows PTAT characteristics in the temperature range of -10°C to 80°C. The total power consumption of the circuit is as low as 1.5 nW. The supply voltage sensitivity of Iref is 2.7 %/V, which shows that the proposed circuit is less sensitive to supply voltage variations. Index Terms - Low voltage, Low power, PTAT current, Switched capacitor. © 2019 IEEE.Item A 0.8 V, 5 nA PTAT current reference circuit with improved supply voltage sensitivity(Institute of Electrical and Electronics Engineers Inc., 2019) Hanumantha Rao, G.; Muhammed Mansoor, C.B.; Rekha, S.This paper presents a low voltage, low power Proportional to Absolute Temperature (PTAT) current reference circuit with improved supply voltage sensitivity. The proposed circuit is designed and laid out in UMC 65 nm CMOS technology and simulated using Cadence Virtuoso. It generates a reference current (Iref) of 5 nA at 0.8 V supply voltage (Vdd) at room temperature (27°C). Composite transistors are used to improve the supply voltage sensitivity when compared to a traditional beta-multiplier circuit. The current reference circuit consumes a power of 8 nW and follows PTAT characteristics in the temperature range of 0°C to 80°C. The supply voltage sensitivity of Iref is 2.6 %/V, which shows that the proposed circuit is less sensitive to supply voltage variations. © 2019 IEEE.Item Low Voltage, Low Power Gm-C filter for low frequency applications(American Scientific Publishers, 2018) Hanumantha Rao, G.; Rekha, S.This paper describes a low voltage, low power Transconductance-C (Gm-C) filter for low frequency applications. A tunable bulk-driven transconductor is proposed to realize the filter. The transcon-ductance (Gm) is tunable from 8 nS to 90 nS, which is suitable for low frequency Gm-C filters. The transconductor consumes a power of 86 nW. To evaluate the performance of the proposed transconductor, a 2nd order Butterworth low pass filter (LPF) is designed. The cutoff frequency of the filter is tunable from 74 Hz to 820 Hz. The filter offers a dynamic range of 52 dB while consuming a power of 248 nW for a nominal cutoff frequency of 456 Hz. The circuit has been designed and simulated in UMC 180 nm technology with a supply voltage of 0.5 V. © © 2018 American Scientific Publishers All rights reserved.Item A 0.3?V, 56?dB DR, 100?Hz fourth order low-pass filter for ECG acquisition system(Elsevier Ltd, 2019) Polineni, S.; Hanumantha Rao, G.; Rekha, S.; Bhat, M.S.This paper proposes an extremely low voltage, low power bulk-driven voltage follower (BD-VF). As an application of the proposed BD-VF, a 4th order low-pass filter (LPF) with cutoff frequency adjustable from 50 Hz to 250 Hz is designed for electrocardiogram (ECG) acquisition systems. The filter is implemented in UMC 180 nm CMOS technology occupying only 0.03 mm2 area. Post layout simulation results show that the filter offers 56 dB dynamic range even with an extremely low supply voltage of 0.3 V. The total power consumption of the filter is 4.8 nW for a cutoff frequency of 100 Hz. The Figure-of-merit (FoM) and capacitance/pole of the filter are 5.7 × 10?15 and 2.2 pF respectively. The proposed filter offers the lowest FoM compared to the state-of-the-art nW-class filters. © 2019 Elsevier LtdItem An area-efficient, large time-constant log-domain filter for low-frequency applications(John Wiley and Sons Ltd vgorayska@wiley.com Southern Gate Chichester, West Sussex PO19 8SQ, 2020) Hanumantha Rao, G.; Rekha, S.This paper proposes a simple technique to increase the time constant of a log-domain filter. By using the proposed technique, the capacitor value can be reduced considerably; hence, overall area of the circuit can be reduced. A second-order log-domain low-pass filter (LPF) is implemented in UMC 65-nm complementary metal-oxide semiconductor (CMOS) technology to validate the proposed technique. It occupies an area as low as 0.005 mm2 and operates with a 0.5-V supply. For a cutoff frequency of 100 Hz, the filter consumes a power of 4 nW. By adjusting the bias current, the cutoff frequency can be linearly tuned from 10 to 500 Hz. The filter has the figure of merit (FoM) of 0.68×10?13 J, which is on par with many designs listed in the literature. The filter uses the lowest capacitance/pole (0.92 pF) among the similar designs given in the literature, which shows that the present design is area efficient. © 2019 John Wiley & Sons, Ltd.Item Low power fast settling switched capacitor PTAT current reference circuit for low frequency applications(ASTES Publishers, 2020) Muhammed Mansoor, C.B.; Hanumantha Rao, G.; Rekha, S.This paper presents a low voltage, low power, fast settling switched capacitor based Proportional to Absolute Temperature (PTAT) current reference circuit. Unlike in a conventional resistor based PTAT current source, the proposed circuit saves a significant amount of silicon area on chip and hence the circuit becomes less susceptible to process variations. It creates a reference current of 1 nA from a 0.5 V power supply at room temperature (27?C). It has PTAT characteristics in the temperatures from ?10?C to 80?C. The circuit draws a very low power of 1.5 nW and exhibits a good supply voltage sensitivity of 3.2 %/V. A startup circuit connected to the PTAT source improves the transient response by reducing the settling time. To test the PTAT current reference circuit, a low power log-domain filter which can be used for biomedical applications is realised and biased with the proposed PTAT current source. Results show that the filter cutoff frequency is constant over temperature variations. The CMOS technology used for designing the circuits is UMC 65 nm and tool used for simulations is Cadence Virtuoso. © 2020 ASTES Publishers. All rights reserved.Item A 0.8-V, 55.1-dB DR, 100 Hz Low-Pass Filter with Low-Power PTAT for Bio-Medical Applications(Taylor and Francis Ltd., 2022) Hanumantha Rao, G.; Rekha, S.This paper presents a power efficient transconductor-capacitor ((Formula presented.)) filter for front-end processing of bio-medical signals. A low voltage, low-power transconductor with improved output resistance is proposed. It offers a transconductance ((Formula presented.)) of 5.85 nS while operating at a supply voltage ((Formula presented.)) of 0.8 V. Furthermore, a low-power Proportional to Absolute Temperature (PTAT) current reference circuit is designed to bias the transconductor and to make (Formula presented.) independent of temperature. It follows PTAT characteristics in the temperature range of ?20 (Formula presented.) C to 70 (Formula presented.) C and is less sensitive to (Formula presented.) variations. A second-order Butterworth low-pass filter (LPF) with a cutoff frequency of 100 Hz is implemented to validate the proposed transconductor and the PTAT circuit. The filter is designed in UMC 65 nm CMOS process and it takes an area of 0.065 mm (Formula presented.). While consuming a power of 47 nW, it offers a dynamic range (DR) of 55.1 dB. Figure-of-merit (FoM) of the filter is as low as (Formula presented.) J, which is found to be on par with the filters reported in the literature. © 2022 IETE.